The present invention relates to a copying apparatus. More particularly this invention concerns a drive arrangement for the paper feed in a copying machine.
A copying apparatus is known such as shown in German published specification No. 2,226,358, whose entire disclosure is herewith incorporated by reference, which feeds paper from a stack at a paper supply past imaging equipment that forms a toner image on the paper and thence past a fuser to an output tray. The imaging equipment can comprise a selenium-coated drum and the fusing equipment can use either a radiant heater or a pressure rollers. Other copying methods may also be used.
Typically the paper is held in a stack underneath a pivotal pickup arm having a roller at one end which is continuously rotated. The pickup arm can be dropped down onto the uppermost sheet in the stack so as frictionally to engage it and slide it off the stack. Each time the pickup arm is briefly dropped down into contact with the uppermost sheet of the stack it therefore slides a sheet off the stack.
Downstream of the pickup arm there is typically provided a pair of pinch rollers which define a closed paper-receiving nip to which the leading edge of the copy sheet is fed. These rollers are rotated stepwise, that is they are periodically rotated to advance the sheet through the machine along the paper-feed path in accordance with the cyclical programmed operation of the machine. The main function of these pinch rollers is to properly align the leading edge of the sheet along the paper path at a perfect right angle to the direction of travel so that when these pinch rollers are rotated the leading edge will not only be properly aligned perpendicular to the paper feed direction, but will also be at the exact desired position for proper registration of the image on the copy sheet.
The master being copied is normally held on a copy window, usually above the above-described mechanism. A scanning device including mirrors and at least one lamp is reciprocal back and forth underneath this window to scan the copy a line at a time. Normally a drive arrangement including a heavy-duty main drive shaft is connected to this scanner so that when rotated in one direction it displaces the scanner across the master and when rotated in the opposite direction it returns the scanner to its starting position. Since this is the heaviest element of the copier the displacement of the other parts of the machine is typically made dependent on the displacement of the scanner.
Thus it is standard practice to provide solenoids and the like operated by cams or the like carried by the scanner drive shaft for synchronously operating the pickup roller and pinch rollers with the scanner. Once during each copy cycle the pickup roller must be dropped down into contact with the uppermost sheet in the stack so as to slide it into the nip of the pinch rollers, and thereafter once during each cycle the pinch rollers must rotate to feed the thus aligned sheet along the conveyor path. Such arrangements are typically rather expensive and failure-prone. If the operation of the pickup arm and pinch rollers is off by the slightest amount of time the copy image will be misaligned on the copy sheet and the copy might be unusable.